Calcined Zn/Al hydrotalcites as solid base catalysts for glycolysis of poly(ethylene terephthalate)



In this research, glycolysis of poly(ethylene terephthalate) (PET) with ethylene glycol (EG) was carried out using Zn/Al mixed oxide catalyst. These mixed oxides were prepared by calcining crystalline Zn/Al hydrotalcites at different calcination temperatures. The samples and corresponding precursors were characterized by X-ray diffraction, BET, Fourier-transform infrared spectra, thermogravimetry/differential thermal analysis, and Hammett titration method. The experimental results showed that Zn/Al mixed oxides obtained from hydrotalcites were found to be more active than their individual oxides for glycolysis of PET. The relationship between catalytic performance and chemical–physical features of catalysts was established. In addition, a study for optimizing the glycolysis reaction conditions, such as the weight ratio of EG to PET, catalyst amount and reaction time, was performed. The conversion of PET and yield of bis(2-hydroxyethyl terephthalate) (BHET) reached about 92% and 79%, respectively, under the optimal experimental conditions. Moreover, it should be noted that Zn/Al mixed oxide not only provided an effective heterogeneous catalyst for glycolysis of poly(ethylene terephthalate), but also presented a novel method for decolorization of discarded colored polyester fabric. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41053.